Originally Posted by
OBoile
This is only true if you're running some very high mileage. For most people, including cyclists doing it as cross training, it's fine and may even have a protective effect.
This is true and on the other hand, if you ride all the time and do not mix in running or walking (older age) then your stride and flexibility for either is decreased and thus cyclist become worse runners and walkers compared to younger times.
It is Not a cardio issue.